Most scientists believe that human beings evolved in Africa, then migrated from the continent to conquer the world.

But researchers from the University of Tubingen in Germany believe that our ancestry might be more complicated - and significant parts of human evolution might have happened in Europe and Western Asia.

The new theory comes after the discovery of an ape's tooth in Bulgaria - dating two million years after the 'pre-humans' were thought to have died out in Europe.

The seven-million-year-old tooth shows that the pre-human had evolved to eat a European diet of grasses, seeds and nuts, rather than fruit.

The Bulgarian pre-human molar revealed that the ape had eaten hard, abrasive objects such as grasses, seeds and nuts. This suggested that it adapted to a change in its surroundings in order to survive

The discovery of the seven million year old tooth has caused scientists to question previous theories about when our simian ancestors disappeared.

It suggests a 'significant' part of human evolution happened in Europe.

Prior to the discovery, the 'youngest' hominid remains found in Europe was a 9.2 million year old fossil unearthed in Greece, which led scientists to conclude that the apes had died out nine million years ago.

This was backed up by climate data showing European had changed from lush green forests to arid savannahs, causing a severe drop in the levels of fruit that formed the bulk of the great apes' diet.

Professor Madelaine Bohme and geologist Philipe Havlik at the archeological site in a sand quarry in Bulgaria. The seven-million-year-old tooth could rewrite our understanding of human evolution

However, a closer look at the Bulgarian pre-human hominid molar revealed that the ape had eaten hard, abrasive objects such as grasses, seeds and nuts.

This suggested that it adapted to a change in its surroundings in order to survive.

Researchers from the University of Tubingen in Germany said the ape's diet was similar to that of African hominids, which only disappeared four million years ago.

Study author Professor Madelaine Bohme, whose findings were published in the Journal of Human Evolution said: 'We now also need to rethink where the origin of humans took place.

'So far, most scientists believe that human evolution happened exclusively in Africa and that humans migrated from Africa to other continents.

'There is increasing evidence, however, that a significant part of human evolution happened outside Africa, in Europe and western Asia.'

The seven-million-year-old pre-human tooth was found in a sand quarry in Azmaka in Bulgaria

She added: 'Until now, the most recent fossil was that of a 9.2 million year old specimen of Ouranopithecus macedonensis from Greece.

'Hominids therefore were thought to have disappeared from Europe prior to 9 million years ago.

'At this time, European terrestrial ecosystems had been changed from mostly evergreen and lush forests to savannah-like landscapes with a seasonal climate.'

'It had been thought that great apes, which typically consume fruits, were unable to survive this change due to a seasonal deficiency of fruits.'

'We found animals typical of a savannah in the fossil-bearing layer: several species of elephants, giraffes, gazelles, antelopes, rhinos, and sabre-toothed cats.

'This discovery suggests that European hominids were able to adapt to the seasonal climate of a savannah-like ecosystem.'

'This conclusion is further corroborated by electron microscope analysis of the tooth's masticatory surface, which reveals that the Bulgarian hominid had consumed hard and abrasive objects like grass, seeds, and nuts.

'In this respect, the feeding behavior of this animal resembles that of later African hominids from about 4 million years ago, such as australopithecids like 'Lucy'